Code Division Multiple Access (CDMA) is a cellular technology originally standardized as IS-95, which competes with GSM technology for dominance in the cellular world. CDMA employs spread-spectrum technology which increases the capacity of cellular systems. CDMA was adopted by the Telecommunications Industry Association (TIA) in 1993. Different variations now exist, with the original CDMA now known as cdmaOne. For example, there is now cdma2000 1xRTT and its variants like 1xEV-DO and 1xEV-DV and 3xRTT Multi-Carrier (MC 3x). These basically refer to variants of usage of a 1.25 MHz carrier channel. For example, MC 3x uses a 3.75 MHz carrier channel. By May 2001, there were 35 million subscribers on cdmaOne systems worldwide.
Third Generation efforts under ITU's IMT-2000 initiative have been motivated in large part by a need to increase the supported data rates over wireless channels. The demand for high rates has not been met by second generation systems since these systems have been defined and designed for only voice and low-rate data. Higher data rates require more bandwidth on the radio channel for transmission.
The cdma2000 standard is a 3rd Generation (3G) solution based on the original IS-95 standard. Unlike some other 3G standards, cdma2000 is an evolution of an existing wireless standard. The cdma2000 standard supports 3G services as defined by the International Telecommunications Union (ITU) for IMT-2000. 3G networks will deliver wireless services with better performance, greater cost-effectiveness and significantly more content. Essentially, the goal is access to any service, anywhere, anytime from one wireless terminal i.e. true converged, mobile services.
Worldwide resources are currently being devoted to roll out third-generation CDMA technology. The cdma2000 standard is one mode of the radio access “family” of air interfaces agreed upon by the Operators Harmonization Group for promoting and facilitating convergence of third generation (3G) networks. In other words, the cdma2000 standard is one solution for wireless operators who want to take advantage of new market dynamics created by mobility and the Internet. The cdma2000 standard is both an air interface and a core network solution for delivering the services that customers are demanding today.
The goal of the cdma2000 standard was to mitigate risks, protect investments and deliver significant performance boosts to operators as they evolve their networks to offer 3G services. Networks based on cdma2000 are backward compatible to cdmaOne (IS-95) deployments, protecting operator investments in cdmaOne networks and providing simple and cost-effective migration paths to the next generation. In addition, cdma2000 networks offer voice quality and voice capacity improvements, and support for high speed and multimedia data services.
The first phase of cdma2000—variously known as 1xRTT, 3G1X, or just plain 1X—offers approximately twice the voice capacity of cdmaOne, average data rates of 144 kbps, backward compatibility with cdmaOne networks, and many other performance improvements. The cdma2000 1xRTT standard can be implemented in existing spectrum or in new spectrum allocations. A cdma2000 1xRTT network will also introduce simultaneous voice and data services, low latency data support and other performance improvements. The backward compatibility with cdmaOne provided by cdma2000 further ensures investment protection.
However, the cdma2000 standard is evolving to continually support new services in a standard 1.25 MHz carrier. In this regard, the evolution of CDMA2000 beyond 1xRTT is now termed CDMA2000 1xEV or 1xEV for short. 1xEV is further divided into two stages: 1xEV-DO and 1xEV-DV. 1xEV-DO stands for 1X Evolution Data Only. 1xEV-DV stands for 1X Evolution Data and Voice. Both 1xEV evolution steps provide for advanced services in cdma2000 using a standard 1.25 MHz carrier. The evolution of cdma2000 will, therefore, continue to be backwards compatible with today's networks and forward compatible with each evolution option.
The 1xEV-DO standard is expected to be available for cdma2000 operators sometime during 2002, and will provide for even higher data rates on 1X systems. Specifically, 1xEV-DO specifies a separate carrier for data, and this carrier will be able to hand-off to a 1X carrier if simultaneous voice and data services are needed. By allocating a separate carrier for data, operators will be able to deliver peak data transmission rates in excess of 2 Mbps to their customers.
It is envisioned that 1xEV-DV solutions will be available approximately one and a half to two years after 1xEV-DO. A goal of 1xEV-DV is to bring data and voice services for cdma2000 back into one carrier. That is, a 1xEV-DV carrier should provide not only high speed data and voice simultaneously, but should also be capable of delivering real-time packet services.
In summary, then, the cdma2000 1xRTT standard is optimized for voice and provides basic packet data services up to 163.2 kbps. This standard is currently being commercialized and will be in the market very soon if not already. The cdma2000 1xEV-DO standard is optimized for data only and provides efficient data service up to 2 Mbps. This standard is to be deployed after cdma2000 1xRTT. Finally, a proposed cdma2000 1xEV-DV standard is to be optimized for both data and voice. Providing simultaneous voice and data services, the goal of such a standard is to provide more spectrum efficiency. Therefore, in terms of the evolution path of the cdma2000 standards for wireless high-speed data transmission, the cdma2000 1xRTT standard is currently progressing towards a cdma2000 1xEV-DO standard which is, in turn, progressing towards an optimized cdma2000 1xEV-DV standard.
In examining the migration path from the 1xRTT standard to 1xEV-DO, those skilled in the art will appreciate that High Data Rate (HDR) technology served as the base technology for 1xEV-DO. Furthermore, the incorporation of the 1xRTT reverse link in 1xEV-DO achieved the objectives of technology reuse as well as providing a cost-effective solution.
In a similar manner, a graceful evolution from 1xEV-DO to 1xEV-DV will minimize re-investments and avoid fragmenting the industry. In this light, 1xEV-DV should be backward compatible to the 1xRTT family of standards and products. In other words, customer and operator investments in CDMA systems should be protected. There should be maximum reuse whenever possible and the 1xEV-DV standard should also consider possible future evolutions such as packet voice.
In addition to the above, any 1xEV-DV proposal should meet the CDMA Development Group (CDG) and Operator's requirements. Specifically, 1xEV-DV should support services with various QoS attributes, simultaneous voice and data on the same carrier, voice capacity enhancement, more spectrum efficiency in packet data transmission and scalability to 3X mode operations.
1xEV-DO increases data capacity but does not allow for voice on the same carrier and therefore does not change the voice capacity of the cdma2000 family. Voice traffic must continue to use 1xRTT. As of Oct. 22, 2001 1xEV-DV proposals have integrated voice and data but voice is handled in the same fashion as 1xRTT thus the voice capacity is unchanged.